1. Field of the Invention
The present invention relates to an apparatus for use in the treatment of scoliosis.
2. Description of the Prior Art
Prior to 1962, scoliosis was treated with various external casts and/or bone grafts. Successive body casts of ever increasing height would be utilized to try to correct the spine from a disorder such as a lateral curve in the spinal column. External braces would still be employed in the treatment of minor scoliosis. However in the event of severe deformity of the spine, major surgery .involving bone grafts and the fusion of several vertebrae would be the only solution. The bone grafts and vertebrae fusion would sometimes cause serious complications throughout the patient's adult life.
In 1962, Paul Harrington proposed the use of implantable stainless steel rods which were placed adjacent the vertebral bodies and hooks on the rods were inserted under the laminae of selected vertebra. An excellent summary of the prior art devices based on the Harrington procedures can be found in U.K. patent application G.B. 2 096 465 A published Oct. 20, 1982 in the name of Kevin A. Bobechko. However it has since been found that it is still necessary to supplement the stainless steel rod with bone grafts as described in the Bobechko patent application.
Canadian Patent 1,262,322 issued Oct. 17, 1989 to Yves Cotrel also described a rod and hook system. Cotrel mounts the hooks with hook brackets to the vertebrae and then the hook brackets can be connected to a pair of rods as shown in FIG. 12. The assembly is rigid in that the hook brackets are locked to the rods against rotational or longitudinal movement. That section of the spine is thus kept rigid. However given the lack of flexibility, and the fact that the loads are completely transferred to the rod assembly, the assembly is not considered sufficiently strong and thus bone graft and fusion of the vertebrae must also be resorted to.